Why are valves located in veins but not in arteries?
A) Valves are located in veins because the wall is thin enough to accommodate the valve.
B) Valves are located in veins to prevent blood from flowing backward because venous pressure is too low to keep the blood moving back toward the heart.
C) Valves are located in veins because they have three wall layers instead of the two layers that arteries have.
D) Valves are located in veins because veins are the only type of blood vessel where blood travels one-way instead of both ways in the vessel.
E) Valves are located in veins because veins see the highest blood pressures so the valves protect the walls of the veins.
Answer: B
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